Superman realizes its vulnerability to kryptonite and retrieves the spear, fatally impaling the creature with it. In its dying moments, the creature kills Superman, who was weakened by kryptonite exposure. Following Luthor’s arrest, Batman confronts him in prison, warning him that he will always be watching.
Superman picks up Batman’s Kryptonite spear, and stabs Doomsday with it. Doomsday stabs him too and Superman is weak enough from all of the various stabbings and explosions that Doomsday’s stab proves fatal.